1. Technical Field
The present invention generally relates to vehicle displays and, more particularly, to methods and apparatus for adjusting the display characteristics of a display unit.
2. Background Information
Display systems are becoming vital components in a wide range of vehicles, including, but not limited to, automobiles, ships, aircraft, and spacecraft. These display systems provide a visual presentation of the information and data detected by sensors and generated by other vehicle systems. This enables the vehicle operator to monitor the vehicle status and operating environment such that the vehicle may be controlled in an efficient manner. For example, navigation information, engine data, structural data, warning information, and radar topographies may be presented by a display system for operator viewing. While operators are generally able to rapidly absorb and process a substantial amount of information produced on a screen of a display system, variations in the display characteristics are generally desirable to ease the operator's task in high workload situations and improve the operator-display interaction.
To appreciate the improvement in operator-display interaction as a result of varying the display characteristics of a display unit, consider the following example. When an airplane is flying into a setting sun, the pilot's eyes adjust by reducing the pupil apertures to compensate for the bright intensity on the horizon. When the pupils are contracted in such a fashion and the pilot looks at the display, the amount of light entering the pilot's eyes from the display unit is limited by the pupils, thereby making it difficult to view the information illuminated on the screen. In addition, when the sun shines into a cockpit window other than the front windshield, or a light source exists behind the pilot, there is a tendency for the light to reflect off of the display unit screen making it difficult for the pilot to view the information on the screen.
To compensate for the above-referenced situations and others not specifically mentioned, most airplane display units have a light sensor, such as a photodiode, affixed to the display unit. The photodiode detects the light intensity level in a semi-defined area in front of the display and generates an electrical signal proportional to the light intensity. The electrical signal generated by the photodiode is provided to circuitry within the display unit for adjustment of the display characteristics (e.g., illumination intensity, color, contrast, and/or the like). When the photodiode detects a low light level in the cockpit, a low illumination intensity of the display unit will be adequate for operator viewing and the circuitry within the display unit adjusts the display characteristics accordingly. However, when the photodiode senses a high light level in the cockpit, a low illumination intensity of the display unit is not generally sufficient to provide ease in operator viewing. Therefore, the circuitry within the display unit directs an increase in the illumination intensity of the display. While this arrangement provides a certain degree of compensation, a problem arises when the photodiode does not detect the full intensity of the light source focused on the upper torso or even the eyes of the pilot. This is typically attributable to the fact that the detection area of the display unit's photodiode is limited to the region directly in front of the display screen, and this may not present an accurate indication of the light that is affecting the pilot's view of the screen.
Some systems compensate through the installation and use of a remote sensor circuit that includes a remote photodiode near the front windshield to measure the light entering the cockpit. While this diminishes the problem associated with the inadequate measurement by the single photodiode affixed to the display screen, several disadvantages are introduced with the addition of a remote sensor circuit. One disadvantage of the remote sensor circuit is the increase in cost, as such components are generally expensive and tend to lack reliability. In addition, as the circuit components used in the remote sensor circuit already reside in the display unit and a photodiode is originally affixed to the display unit, a duplication in circuitry and photodiodes results. Furthermore, since the remote sensor circuit receives power and transmits signals through a cable attached to the connector on the display unit, connector pins are taken that might otherwise be available for other functions.